#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int main(void)  {

	fd_set rfds;
	struct timeval tv;
	int retval;

	/* Watch stdin (fd 0) to see when it has input. */
	FD_ZERO(&rfds);
	FD_SET(0, &rfds);

	/* Wait up to five seconds. */
	tv.tv_sec = 5;
	tv.tv_usec = 0;

	retval = select(1, &rfds, NULL, NULL, &tv);
	
	printf("come from select().\n");	
	
	if (retval == -1)
		perror("select()");
	else if (FD_ISSET(0, &rfds)) {
		printf("Data is available now.\n");
	} else
		printf("No data within five seconds.\n");

	exit(EXIT_SUCCESS);

}
